Transformer.



C. L12-G, VFormscufI l TRANsfoBMEm APPucATlouj msn A1115.v 1. '1911;

,1 1,227,415. I Patented my '22, 1911.

Y rf/V fri ATTORNEY UNITED STATES PATENT CHARLES LE G. FORTESCUE, F PITTSBURGH, PENSYLVANIA, ASSIGNOB T WESTING- HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION 0F PENN- SYLVANIA.

TRANS FORMER.

Specification of Letters Patent.

Patented May 22, 1917.

A ain, and' a residentof Pittsburgh, 'in the mized by reason of the core members having county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Transformers, of which the following is a specification.

My invention relates to electrical apparutus und particularly to polyphase transformers.

The object of my invention is to provideA n particularly simple and inexpensive threephase transformer which shall be so arranged and proportioned as to utilize its magnetizable core member to a maximum extent.

According to my invention, the magne tizable core members of polyphase transformers may be worked at uniform ux densities throughout. This permitsA of a very eflicient construction for transformers because each portion of the magnetizable core members will be worked at the same maximum flux density, thereby requiring a minimum amount of material for the core structures. Again, the iron losses are minino portions that are worked either'at extremely high or low, and, consequently', inefficient flux densities. By embodying my invention in transformer structures, I p rovide transformers which operate at high eliiciencies, and which, at the same time, require considerably less material than heretofore utilized .in polyphase transformers of similar, capacities.

Figure 1 of the accompanying drawin is an elevation of a transformer' arrange in accordance with my invention, the coils being shown in cross section. Fig. 2 is a dia- ,gi-animatie view showing the circuit connections' for the coils shown in Fig.`1'.

Referring to thel drawings, the three phase T-connected transformer here shown comprises a core member having an outer rectangular portion 1, and a central cruciform portion composed of legs 2 and 3, second ary windings 4 and 5 and primary wi-ndings 6 and 7.

I propose. to use the well knownScott tr sformer connection in my transformer inlorder that advantage may be taken of the phase diierence in the fluxes generated by the T-connected windings. The active length of the windings .4r-and 6 may be oonsidercd as being 100 per cent. Then, to secure terminal volta es having proper values and proper mutua phase differences, the active lengths of the windings 5 und 7 must be 86.6 per cent. This relationship between the active lengths of the windin s comprising the Scott connection is wel known in the art.

The primary coil windings 4 and G are dis posed in one set 0f openings. in the core member of my transformer, and, similarly, the secondarv coilzwindin 5 and 7 are disposed n the other set o openings in the same core. I desire to have the dimensions of one pair of sides ofthe`core openings equal, as shown in'Fig. 1. Consequently, the dimensions of-'therother pair of sides of the core openings are in' the ratioof 100 :86.6 because of the' aforementioned ratio bef tween the' activeal'exigths of the respective windings. By apportioning' the insulation forV the windings v5 and 7, and choosing a proper ldimension for the copper conductors thereof, theV abovelmentioned ratio may be approximated and defined as being 10:8. However, it will be understood that, if the windings were similar and differedl only in their active lengths, the ratio between the sides of the respective core openings would be 100:86.6,`but, for convenience, I, have modified the structure so as to change the said ratio to 10:8.' "i

Equal uantities of iux are generated by the energization 0f the windings 4-6 and the windings 5-7. Therefore, the cross sectional area of the leg 3, which carries all the flux is twice thatof the core portion 1 which carries one-half of the flux ,by reason of the ux dividing into two. equal portions at the junction between the core leg?) and the portion 1 of the fcore. Inasmuch as the-iux generated by the energization of the coils A 4 and 6 is equal to, and 90 degrees displaced in phase from, the flux generated by the coils 5 and 7, the resultant flux flowing in the core leg 2 is substantially equal ,to 1.4 times that flowing in the core 'portion 1. In order to insure that each portion of the core is worked at the same flux density throughout, the cross-sectional area of the core leg 2 i.; substantially one and four tenths timesthat of the portion 1, and the cross-sectional area of the leg 3 is substantially twice that of the portion 1. For convenience m construction, the leg 3 of. the cruciform portion may be divided in length by the le 2 substantiallyin thematic of 10:8, and t e turns of the coils'4 and 5 and 6 and 7 bear substantially the 'lxne ratio to each pther and surround the portions of the core leg 3 to which they correspond.

As shown in Fig. 2 one terminalof the winding 5 is connected to the middle point of the winding 4 and the corresponding terminal of the winding 7 is connected to the middle point of the. winding 6, the terminals of the winding 4 and the free terminal of the winding 5 constituting three-phase points which may be connected to circuit conductors 8, 9 and 10. The terminals of the windings 6. and i are similarly connected to circuit conductors 11, 12 and 13.

The circuit connections shownin Fig. 2 of the drawing und specified in the plieceding paragraph are well known threeaSe connections for a transformer having two primaryand two secondary windings.

I claim as my invention: y

1. A three-phase T-eonnected transformer comprising a core member having an outer portion and a central cruciform portion and coils divided between the two parts o one of the cruciform .core legs substantially in the ratio of 8 :10.

2. A three-phase T-connected transformer comprising an outer rectangular core portion and a crucform inner portion, the cross sectional area of one of the legs of the crucilform portion being' substantially twice that of the outer portion, andthe cross Sectional area of the other leg being substantially one ,l

and four tenths that of the outer portion, und coils mounted on two parts of one of the core legs.

3. A, three-phase T-connected transformer comprising an outer rectangular corre portion and a cruciforin inner ortion, the cross sectional area of one of the ege of the cruci form portion being substantially twice that of the outer portion, and the cross sectional area of the other leg being substantially one and ,four tenths that of the outer portion and coils divided between the two parts ci one of the crucform core legs substantially in the ratio of 8 :10.

`4. A.threephase transformer comprising a core member-,having an outer rectangular portion and a central cruciform portion', one le of the cruciform portion dividing the ot er substntially in the ratio of 8:10 and the cross sectional area of one of the cruciform core llegs being substantially twice that of the outerA portion, and the cross sectional area of the other leg being substantially one and four tenths that of the o uter portion, and coils located on the parts of the core which are divided in the ratio of 8:10, the turns ofthe coils bearing substantially the same ratio to each other as the parts of the core on which they are located.

In testimony whereof,- I have hereunto subscribed my name this 31st day of July, 1911.

CHARLES LE G. FORTESCUE.

' Witnesses:

R. J. DmnnonN, B. B. 

